The spark end is introduced in a controlled manner by the arrangement of a primary end short-circuit switch. In this way, the method is based on the ignition system having a shortened spark duration such as is known from DE 196 49 278. The method of the invention can also be applied to other ignition systems which shorten the ignition spark via a primary end short circuit with other means such as npn-transistors or thyristors.
An ion current measurement can be coupled with the ignition system as is known from DE 38 83 009 T2. The ion current measurement measures the ion current in the combustion chamber via the secondary end of the ignition coil and/or of the ignition transformer by means of the spark plug.
The operation of the switchoff of the ignition spark itself needs a certain time duration which can be disturbing under circumstances for the ion current measurement. Furthermore, the ignition coil and/or the ignition transformer and the short-circuit switch become unnecessarily warm because of the residual energy.
In view of this background, it is an object of the invention to:
minimize disturbances on the ion current measurement caused by the switchoff current; PA1 to reduce the heat in the short-circuit switch and in the ignition transformer; PA1 to keep the electrode wear low; and, PA1 to ensure a reliable and rapid switchoff of the spark.